1. 1

2. Question: Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse? 2

3.  Surface area (plasma membrane surface) is determined by A = L x W  Volume of a cell is determined by V = L x W x H V = L x W x H volume surface area  Therefore, volume increases FASTER than the surface area 3

4.  When the surface area is no longer great enough to get rid of all the wastes and take in enough nutrients, food and water… then the cell MUST divide  Therefore, the cells of an organism are close in size 4

5. Question: Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse? 5 About the same size, but … The elephant has MANY MORE cells than a mouse!

6. Osmosis is a special case of diffusion Osmosis involves the diffusion of water through a membrane The membrane may be: Artificial (non-living) - Cellophane Natural - Cell Membrane

7. The membrane must allow water molecules to diffuse through. The cell membrane is permeable to H 2 O. If a dilute solution is separated from a concentrated solution... water will pass from the dilute to the concentrated solution.Permeability

8. Osmosis dilute solution concentrated solution membrane More water passes from dilute to concentrated......until concentrations become equal level rises level falls

10. Common misconception: Water does happen to pass in BOTH directions... it just passes faster from the dilute to the concentrated solution.

11. Remember... Water molecules undergo diffusion. H2OH2O

12. membrane watersugar solution There are as many water molecules on the right as there are on the left. Many of them on the right are attached to sugar molecules and are not free to move.

13. Because there are more freely moving water molecules on the left, more H 2 O diffuses through the pores of the membrane from left to right. Molecular movement

14. Next slideAnimation

15. Cytoplasm functions as a fairly concentrated solution. Osmosis in Animal Cells

16. There is a greater concentration of free water molecules outside the cell than inside…...so water diffuses into the cell by osmosis and the cell swells up

17. If osmosis continued, the animal cell would burst! This would be bad news for animals  Consequently, there are processes in the animal’s body which control osmosis... This is done by keeping the concentration of body fluids inside the cell the same as it is outside

18. In fresh water fish, blood is more concentrated than the surrounding water As a result the fish takes in water by osmosis Not so much through the skin - (too) thick – but through the gills, which have a very thin membrane Trout Osmosis Adaptation: Fresh water fish - Gills Perch

19. The fish gets rid of the excess water by means of its kidneys gills absorb water by osmosis blood carries water to kidneys kidneys expel excess water......in the form of dilute urine heart

20.  Found in unicellular protists like paramecia  Regulate water intake by pumping out excess H 2 O(homeostasis)  Keeps the cell from lysing (bursting) 20 Contractile vacuole animation

21. A solution can be… 1. Hypotonic 2. Isotonic 3. Hypertonic 21

22.  Hypo = less, (think hypothermia) Tonic = dissolved particles  Hypotonic Solution = Solute concentration lower outside than inside the cell The outside of the cell has LESS solute, MORE free H 2 O

23. http://www.chem.ufl.edu/~itl/4411/colligative/F G13_022.GIF  Water moves into cell from solution.  Cell expands (and may burst)

24.  The concentration of solutes is the same on either side of the membrane. Both sides have the same amount of solutes and free H 2 O!  No NET water movement.  This is the ideal situation!

25.  Hyper = more (think hyperactive) Tonic = dissolved particles  Hypertonic Solution: Solute concentration higher outside the cell than inside the cell. The outside of the cell has MORE solute, LESS free H 2 O http://cdn.innovateus.net/preset_4/hypertonicbloodcell.png

26.  Water moves out of cell into solution.  Cell shrinks and becomes shriveled

28. Comprehension Question: What would happen if a nurse gave a patient an IV with a pure water solution? Draw it, explain it!

29. Comprehension Question: Survival Tip: If stranded at sea, people are cautioned not to drink the ocean water, no matter how thirsty they may become. Draw it, explain it!

30. Osmosis and Plant Cells Cytoplasm functions as a fairly concentrated solution. Plant cellsPlant cells are surrounded by a strong, rigid cell wall which prevents the cell from taking on too much water and exploding.

31. Cell membrane acts as a selectively permeable membrane The vacuole contains a solution of salts and sugars If there is water outside the cell, it will diffuse by osmosis through the plasma membrane into the vacuole Cell wall is freely permeable to water The vacuole will expand, pushing the cytoplasm outwards against the cell wall

32. The cellulose cell wall cannot stretch, so the vacuole cannot continue to expand But the pressure of the vacuole against the cell wall makes the cell very firm A plant cell in this condition is said to be turgid If all the cells in the plant are turgid, the plant will be firm and upright and the leaves would be expanded

33. cell wall cytoplasm and cell membrane vacuole The cell absorbs water by osmosis........but the cell wall stops the cell from expanding any more Plant cells

34. These cells are short of water; the tissue is limp and the plant is wilting The cells have taken up water by osmosis; the cells are turgid and the tissue is firm Limp (Plasmolyzed) VS. Turgid Tissue

35. (1)Limp/ Plasmolyzed (2) turgid

37. The color of cell sap in these two cells differ. What does this say about the concentrations of the cell sap? What will happen? Osmosis between Plant Cells

38. If the concentration of the cell sap is greater in one cell than in its neighbor, water will pass by osmosis from the less concentrated to the more concentrated. cell sap more concentrated cell sap less concentrated

39. Plasmolysis in Red Onion Cell  http://www.youtube.com/watch?v=Sw87Q53 NZLI http://www.youtube.com/watch?v=Sw87Q53 NZLI  http://www.youtube.com/watch?v=gYbt7hhI xPo http://www.youtube.com/watch?v=gYbt7hhI xPo  http://www.youtube.com/watch?v=x4il3cHhq hY http://www.youtube.com/watch?v=x4il3cHhq hY

40. Exposure to extremely hypertonic environments can kill a plant. EX: pees Your dog creates spots of dead lawn where he pees. urine The urine is hypertonic to the interior of the cells that make up the blade of grass water Large amounts of water are drawn out of the grass, killing it!

41. 1.Osmosis 2.Contractile Vacuole 3.Hypotonic Solution 4.Hypertonic Solution 5.Isotonic Solution 6.Plasmolyzed 7.Turgid